Heretofore, a multi-piece oil ring has been used in the internal combustion engine, wherein the multi-piece oil ring comprises: an oil ring main member in which two rails are connected together by a columnar part and which has a roughly I-shaped cross section; and a coil expander which is placed in an inner circumferential groove formed on the inner circumferential surface of the columnar part of the oil ring main member, and which applies force to the oil ring main member in such a way as to press the same outwardly in the radial direction of the oil ring main member. With respect to such a multi-piece oil ring, it is required to reduce the oil consumption and to reduce the friction, and various developments has been made in order to reduce the oil consumption and to reduce the friction.
For instance, in the Patent Literature 1, the disclosed is an oil ring for the sake of reducing the oil consumption, in which each of the two rails of the oil ring main member has an individual sliding section protuberance, the tip of which forms an elevation.